SuperKEKB
current status and future plan
K. Shibata(on behalf of SuperKEKB Accelerator Group)2020.11.09
B2GM
Inter-University Research Institute Corporation High Energy Accelerator Research Organization (KEK)
大学共同利用機関法人 高エネルギー加速器研究機構 (KEK)Highlight from 2020ab run• Main missions of 2020ab run;

• Physics run toward more than 100 fb−1
• Demonstration of crab-waist collision scheme• Overview of 2020ab run;• From 25/Feb. to 1/July.
• Beta squeezing:• Mainly βy* = 1 mm, βx* = 60(HER)/80(LER) mm• Finally βy* = 0.8 mm, βx* = 60 mm
Smallest βy* in the world !!

• Crab-waist:• Cabling work for HER crab-waist (20-23/April)• LER : 0 % → 40 % → 60 % → 80 %• HER : 0 % → 40 %• Luminosity:• Peak Lumi. : 2.4 × 1034 cm−2⋅s−1 (NEW World Record!!)• βx/y* : 60/1mm (HER), 80/1 mm(LER)• Crab Waist : 40% (HER), 80% (LER)• Current : 610 mA (HER), 720 mA (LER)
4.9 spacing (3-6 mix), 2 trains, 978 bunches• Delivered Integrated Lumi : ∼74 fb−1
2020/11/9

B2GM2

Specific luminosity (2020ab)• Luminosity
𝐿𝐿 =Y. Ohnish

𝑁𝑁+ 𝑁𝑁− 𝑛𝑛b 𝑓𝑓0∗4𝜋𝜋𝜎𝜎x,eff𝜀𝜀y 𝛽𝛽y∗

• Specific luminosity
𝐿𝐿
𝐿𝐿sp =∝𝐼𝐼b+ 𝐼𝐼b− 𝑛𝑛b1

𝜀𝜀y 𝛽𝛽y∗𝜎𝜎y∗• Lsp depends on 1/σy*.
• Lsp doesn’t depend on Ib+Ib-.
• However, it was observed that Lsp decreases
as Ib+Ib- increases.
Beam blowup due to Beam-Beam effect at large Ib+Ib-.
2020/11/9

B2GM

3

Luminosity performance
Y. Ohnish

2020/11/9

B2GM4

Major works during summer shutdown• Installation of new D03V1 collimator in LER• Replacement of Tantalum jaws in D06V1 to Carbon jaws (Low-Z collimator)• Installation of new skew-quadrupole (skew-Q) magnet in injection kicker section of LER• Preparation and improvement of various beam tuning knobs to control rotatable sextupole
magnets of LER• Visual inspection of the inside of beam pipes of electron beam transport line.
• Already reported by Mori_san• Others• Regular maintenance of various power supplies and components• Visual check of jaws in HER collimators• Removal of gate valves that may cause vacuum pressure spikes in HER• Installation of new bellows chambers with high SR-masks into Wiggler Sections in LER• Replacement of mirror of SR beam size monitor in HER• Etc.

2020/11/9

B2GM5

Collimator works• Installation of newD03V1 collimator in LER• In-situ baking was performed after installation to reduce the pressure.
• Conventional Tantalum jaws are installed into D03V1 collimator.

• Replacement of Tantalum jaws in D06V1 to Carbon jaws (Low-Z collimator)• In-situ baking was performed after installation to reduce the pressure.
• Removed Tantalum jaws were damaged during Phase-3 2020ab.

• Visual check of jaws in HER collimators• It was found that there are many damaged jaws, though it is unknown when they weredamaged.

LER: D03 arc section
D04 wiggler section
D06 arc section
Installation of D03V1(in-situ baking)D04 bellows
replacements
D06V1 head replacement(in-situ baking)Installation of EC test
chambers

Carbon headIn-situ baking

D06V1 collimator

T. Ishibashi
2020/11/9

B2GM6

Installation of skew-Q magnet in LER• Installation of new skew-quadrupole (skew-Q) magnet in injection kicker section of LER.
• For correction of X-Y coupling due to Injections kickers.
• Its effectiveness has been proven with permanent magnets during Phase-3 2020ab.
••••

Improvement of injection efficiency
Reduction of injection BG duration
Suppression of luminosity drop during injectionetc.

New skew-Q magnet

skew-Q magnet(trial model with permanent magnets)
2020/11/9

B2GM

7

Superconducting Cavity problem (HER)• Abnormal high pressure was observed in Superconducting Cavity (SCC) D11D in HER
immediately before 2020c run.

• Small leakage was detected in D11D.
• In order to reduce the pressure near D11D, two additional pumps were installed on both sides of D11D.
• The pressure in D11D has been kept low enough to operate HER normally so far.

• It was decided not to use D11D for beam operation• D11D is detuned during 2020c operation.
• Accelerating voltage is compensated by other SCCs.
• D11D will be replaced with a spare cavity during this winter shutdown.

CCG voltageto scale pressure [V]SCC D11DAdditional pumps
2020/11/9

B2GM8Vacuum work locations during summer shutdown
HER: D04 SRM section
D08 Inj. section

LER: D03 arc section
D04 wiggler section
D06 arc section
Installation of D03V1(in-situ baking)

SRM section
D04 bellows replacements

D06V1 head replacement(in-situ baking)

GV removal

Installation of EC test chambers

2020/11/9

B2GM

9Phase-3 2020c Beam Commissioning• Main missions of Phase-3 2020c run;

• Physics run toward more than 40 fb−1 (only in2020c)• Challenge to Peak Lumi. of ∼4 × 1034 cm−2⋅s−1• Doubling luminosity world record• With beam currents of 0.75 – 1 A• Beta squeezing : βx/y* = 60/0.6 mm• Overview of 2020c run (until 8/Nov.);• Operation time : 60 days (19/Oct. - 18/Dec.)• Vacuum scrubbing : 19/Oct. - 27/Oct.
• Beta squeezing & Crab waist:

vacuum scrubbing• HER βy* = 1 mm, βx* = 80 mm, Crab-waist 40 %• LER βy* = 1 mm, βx* = 60 mm , Crab-waist 60 %• Finally we came back to Physics Run with 1mm-βy*.

• Luminosity (until 8/Nov. 12:00):• Peak Luminosity : 1.4 × 1034 cm−2⋅s−1• Integrated Luminosity (delivered) : 4.7 fb−1
2020/11/9

B2GM

10

Luminosity performance
Y. Ohnish• Target stability of machine performance : 1.5 fb−1/day
2020/11/9

B2GM

11

Operation plan of Phase3 2020c
Y. Ohnish

Now we are here.

2020/11/9

B2GM

12

Challenges in 2020c• Raising peak luminosity• Further βy* squeezing down to 0.6 mm• Collision tuning to suppress beam-beam blow-up
at high bunch current products• Raising beam current• Reduction of background noise to Belle IIdetector• New vertical collimator D03V1 in LER• New carbon jaws of D06V1 (low-Z collimator) inLER• Suppression of X-Y coupling at injection kicker
section of LER• New skew-Q magnet at injection kicker section• Extension of very short beam lifetime• Overcoming difficulties in correction of beamoptics• Maintaining aged hardware including buildings• Etc.
2020/11/9

B2GM

13

Machine studies
News flash of recent machine studies
1. Carbon-head (Low-Z) collimator
D06V1 in LER• It was confirmed that low-Z collimator
worked well to suppress BG.

Carbon head

2. Skew-Q magnet at injection section
in LER• It was confirmed that new skew-Q
magnet installed at injection section ofLER worked well to suppress X-Y couplingof injected beam.
• BG due to injected beams were reduced.
• BG duration was also reduced.

New skew-Q magnet
without skew-Q

S. Teruiwith skew-Q

Vertical oscillation of injected beam was well suppressed.
2020/11/9

B2GM

14

Maintaining aged hardware• Anti-aging measures for old components and facilities are indispensable for stable operation ofSuperKEKB.
• Potential risk of long-term failure increases rapidly.
• Budget for beam operation will have to be allocated to maintenance costs.
• This is not a problem just for this term, but a long-term problem.

Examples of aging:
Erosion of Klystron cooling towers

Water leakage from old flow sensors

Leakage of roof of power supply buildings

Others: Frequent failures of old power supplies for magnets
Heat up of power supply building due to poor thermal barrieretc.
2020/11/9

B2GM

15

Long-term planY. Suetsugu• Plan proposed for MEXT Roadmap2020

MEXT : Ministry of Education, Culture, Sports, Science and Technology• Based on results obtained so far andexpected budged.
• QCS upgrade is newly proposed.

• New goals:• Integrated luminosity : 50 ab−1 around 2030
• Peak luminosity : ∼6 × 1035 cm−2⋅s−1• βy* squeezing: 0.5 mm before IR upgrade,
0.3 mm after that

• Beam currents (LER/HER):∼2.5A/∼1.8A before RF upgrade∼2.9A/∼2.1A after that

• Required investment in equipment• IR upgrade(QCS, its beam pipes, etc.)• Partial RF-power upgrade (2 stations)• Beam collimator upgrade• Linac upgrade• Belle II upgrade
2020/11/9

B2GM

16

IR upgrade plan
• Motivation• Strong beam-beam effects in high bunch current region

H. Nakayama• Resent studies indicate that one promising countermeasure ismodification of QCS to avoid interference between its magnetic fieldand Belle II solenoid field for LER.

• Narrow physical aperture in QCS beam pipes• QCS quenches caused by unstable beam hits have been observed.
• If we squeeze βy* to less than 0.5 mm, it will be difficult to protect
QCS by using collimators.

• Large background noise from QCS beam pipes• At present, background in Belle II is larger than expected.
• One of main background sources is hit of beam halo on the QCS
beam pipes.
• Background will become larger as βy* is further squeezed.

→ Modification of QCS magnets and QCS beam pipes
with large aperture is required.

• Accelerator Review Committee requested an investigation
into the feasibility and effectiveness of IR upgrade plan
before making final decision. (within ∼2 years)• Design works of new QCS and its beams pipes started, andthey are ongoing now.
• IP bellows, RVC lock flanges and QCSR front plate should
be modified too.
2020/11/9

B2GM

RVC lock flange

QCS beam pipes(front end)

IP bellows
172021a operation plan
• Winter shutdown• From 18/Dec./2020 to 16/Feb./2021• Replacement of SCC D11D
• Replacement of 66 kV high-voltage power supply lines• By the end of March 2021

• Operation time of this JFY (Apr. 2020 –Mar. 2021) willbe ∼6.5 months.
• Toward more than 240 fb−1 in total• Target peak lumi. : ∼6.5 × 1034 cm−2⋅s−1• 2021a run• Beam currents : ∼ 0.9 A• Beta squeezing : βx/y* = 60/0.6 mm• From 16/Feb. to 31/Mar.

• Operation cost will be covered with an extra budget fromDirector.

• LER operation will start on 16/Feb.
• HER operation will start on ∼24/Feb.

• It depends on D11D replacement work.

Y. Suetsugu
2020/11/9

B2GM18

JFY2021 run plan
• JFY2021 budget request process is ongoing.
• MEXT has asked to align JFY2021 budget request to the plan submittedfor the MEXT Roadmap2020.
• 5.7 months of operation in JFY2021• Taking account of long shutdown for PXD replacement from Jan. 2022.

JFY: Japanese Fiscal Year, from April to March of next year.
MEXT : Ministry of Education, Culture, Sports, Science and Technology
Y. Suetsugu

preliminary

2020/11/9

B2GM

19

Summary• 2020c run• From 19/Oct. to 18/Dec.
• Vacuum scrubbing before physics run completed successfully.
• Physics run with βy* = 1 mm has been resumed.

• 2020 winter shutdown• SCC D11D will be replaced with a spare cavity.

• 2021a run• From 16/Feb. to 31/Mar.
• Target peak luminosity : ∼6.5 × 1034 cm−2⋅s−1• Beam currents : ∼ 0.9 A• Beta squeezing : βx/y* = 60/0.6 mm• Long-term plan proposed for MEXT Roadmap2020• New luminosity targets :• Integrated luminosity : 50 ab−1 around 2030
• Peak luminosity : ∼6 × 1035 cm−2⋅s−1• IR upgrade & Partial RF-power upgrade are required.
• JFY2021 budget request process is ongoing.
2020/11/9

B2GM

20

Fin.

Thank you for your attention.

Inter-University Research Institute Corporation High Energy Accelerator Research Organization (KEK)
大学共同利用機関法人 高エネルギー加速器研究機構 (KEK)Backup

2020/11/9B2GM22

Vacuum scrubbing since Phase1
LER

2020/11/9

HER

B2GM

Y. Suetsugu

23